In some mechanical apparatuses, such as gas turbine engines, it may be required to have tubes pass through compartments exposed to different pressures and/or temperatures. Accordingly, various arrangements have been devised to allow such fluid communication through compartments. One known arrangement has oil tubes including seals at interfaces with different cavities (external, buffer and oil). This arrangement may have the weakness of possible leakage at the seals, especially when the surrounding external air temperature is high. Another arrangement has local bridges between the cavities through which the tube passes and brazed at opposite ends. In such an arrangement, thermal stresses/local deformations may be created by the local bridges between a hot external wall and cold internal wall.